Lecture 7 (endocrine system) Flashcards
Hormones? (in general)
Most hormones are chemicals secreted by a group of cells in one part of the body and carried through the bloodstream to other parts of the body, where they act on specific target tissues to produce specific physiological effects.
What does it mean that hormones act gradually?
Activating behavioral and physiological responses hours or weeks after entering the bloodstream. The changes may persist for days, weeks, or years.
Do hormones act as a switch?
No, they tend to act by changing the intensity or probability of evoked behavior, rather than as a switch.
What can hormones affect?
Hormones can affect only those cells that possess corresponding receptor proteins to recognize the hormones and alter cell function.
What are the three ways in which hormones are regulated?
Autocrine feedback, target cell feedback, and brain regulation.
Autocrine feedback?
is regulated by negative feedback.
Target cell feedback?
example: insulin and glucose. It is a biological response which gives feedback to the endocrine cell if it has to secrete more or less hormone.
Brain regulation?
a biological response. But the difference is that it will lead back to the brain so it can decide if it needs to secrete more or less hormone.
How is the endocrine system regulated by hypothalamus?
- Directly: neuroendocrine products from hypothalamus by the posterior pituitary gland.
- Indirectly: through releasing hormones which regulates the anterior pituitary gland.
What is hypothalamus itself regulated by?
by synaptic inputs from other brain parts and the body. Isn’t covered by the blood-brain-barrier.
How is the endocrine system regulated by pituitary?
Regulates hormone secretion from other endocrine glands.
- The posterior part doesn’t produce hormones. The hormones are transported via axons in the neurosecretory cells.
*The anterior part is regulated by releasing hormones from the hypothalamus. It secretes tropical hormones which regulates other hormones.
Posterior pituitary and hormone secretion?
o Oxytocin: stimulates contraction of uterine muscles; stimulates release of milk by mammary glands.
o Vasopressin (AVP), or antidiuretic hormone (ADH): stimulates increased water reabsorption by kidneys; stimulates constriction of blood vessels.
Anterior pituitary and hormone secretion?
o Growth hormone (GH): stimulates growth
o Thyroid-stimulating hormone (TSH): stimulates the thyroid
o Adrenocorticotropic hormone (ACTH): stimulates the adrenal cortex
o Follicle-stimulating hormone (FSH): stimulates growth of ovarian follicles and of seminiferous tubules of the testes.
o Luteinizing hormone (LH): stimulates conversion of follicles into corpora lutea; stimulates secretion of sex hormones by gonads.
o Prolactin: stimulates milk production by mammary glands.
Hypothalamus and hormone secretion?
Oxytocin; vasopressin.
Pineal and hormone secretion?
Melatonin: regulates seasonal changes; regulates puberty.